Focus on National 5 Unit 1 - Chemical Changes and Structure Name Class
Nuclide Notation mass number b atomic number b ax Symbol Number of protons = Number of electrons = Number of neutrons = atomic number atomic number IF NEUTRAL atomic number + number of -ve charges IF NEGATIVE atomic number number of +ve charges IF POSITIVE mass number atomic number 7 p = Li 3 e = 19 p = F 9 e = 39 p = Ca 20 e = 37 p = Cl 17 e = 235 p = U 92 e = 18 p = X e = 56 p = Y e = 27 p = Z e = 10 30 14 X is Y is Z is 7 p = Li + 3 e = 19 p = F - 9 e = 39 p = Ca 2+ 20 e = 15 p = N 3-7 e = 235 p = U 3+ 92 e = 31 p = X 2- e = 9 p = Y 2+ e = 23 p = Z + e = 15 5 12 X is Y is Z is Culloden academy chemistry department 2
Writing formulae Is it an element or a compound? element compound Is it a diatomic element? Does it have a prefix? yes no yes no Write the symbol followed by a subscript 2 e.g. F2 Write the symbol on it s own e.g. Mg Write the symbols with the prefixed element with the appropriate number e.g carbon dioxide CO2 Does it contain a complex ion? no yes Write the formula using the symbols of the elements and the valency rules e.g. copper(ii) oxide CuO Write the formula using the formula of the complex ion (s) from the data book, the symbol of the other element and the valency rules e.g. sodium nitrate NaNO3 Valency rules 1. write down symbols 2. work out valencies 3. simplify if possible 4. cross over and write as subscripts to the right of the symbols (nb you may need to use brackets with complex ions) Group 1 2 3 4 5 6 7 0 number Valency 1 2 3 4 3 2 1 0 Culloden academy chemistry department 3
For example: Magnesium chloride Bromine Aluminium sulphate MgCl2 Br2 Al2(SO4)3 Write the formulae for the following substances 1. nitrogen dioxide 2. potassium chloride 3. magnesium bromide 4. magnesium nitride 5. sulphur trioxide 6. copper (I) chloride 7. sodium phosphate 8. potassium hydroxide 9. ammonium chloride 10.lead (II) nitrate 11.uranium hexafluoride 12.nitrogen Culloden academy chemistry department 4
Writing ionic formulae Ionic formulae can be written for: IONIC compounds only Not for: Covalent compounds Elements Use prefix rules as before to write formula, but instead of using just symbol of the element, use the ionic symbol for simple ions or the ionic formula for complex ions. e.g. Mg 2+ SO4 2- Na + Cl - NH4 + O 2- If you need to write a subscript number to the right, you must use brackets e.g. (Mg 2+ )3 (SO4 2- )3 (Na + 2 (Cl - )2 (NH4 + )3 (O 2- )3 Charges DO NOT simplify or cancel out. The total number of positive charges must equal the total number of negative charges. For example: Magnesium chloride Mg 2+ (Cl - )2 Aluminium sulphate (Al 3+ )2(SO4 2- )3 Culloden academy chemistry department 5
Write the ionic formulae for the following substances: 1. sodium phosphate 2. potassium hydroxide 3. ammonium chloride 4. lead (II) nitrate 5. ammonium carbonate 6. caesium fluoride 7. lithium chloride 8. magnesium nitrate 9. potassium hydroxide 10. ammonium bromide 11. rubidium fluoride 12. magnesium sulphate Culloden academy chemistry department 6
Balancing equations You can only balance equations by putting large numbers in front of formulae DO NOT change the formulae. e.g. Mg(OH)2 + 2HNO3 Mg(NO3)2 + 2H2O Balance these equations: 1. CO + O2 CO2 2. P + Cl2 PCl3 3. C + Br2 CBr4 4. C4H8 + O2 CO2 + H2O 5. H2O2 H2O + O2 6. Mg + AgNO3(aq) Mg(NO3)2(aq) + Ag 7. NaOH + H2SO4 Na2SO4 + H2O 8. AgNO3 + BaCl2 Ba(NO3)2 + AgCl 9. Na + H2O NaOH + H2 10. Al + Cl2 AlCl3 11. Fe + O2 FeO 12. Ca + H2O Ca(OH)2 + H2 Culloden academy chemistry department 7
Gram formula mass Ca(NO3)2 6 x O = 6 x 16 = 96 2 x N = 2 x 14 = 28 1 x Ca = 1 x 40 = 40 = 164g 1. Calculate the gram formula mass of calcium bromide, CaBr2 2. Calculate the gram formula mass of sodium oxide, Na2O 3. Calculate the gram formula mass of magnesium carbonate, MgCO3 4. Calculate the gram formula mass of ammonium nitrate, NH4NO3 5. Calculate the gram formula mass of aluminium nitrate, Al(NO3)3 6. Calculate the gram formula mass of ammonium phosphate, (NH4)3PO4 7. Calculate the gram formula mass of calcium hydroxide, Ca(OH)2 8. Calculate the gram formula mass of aluminium sulphate, Al2(SO4)3 Culloden academy chemistry department 8
Calculations using the mole and gfm m n gfm where: m = mass, in grams number of moles gfm = gram formula mass 1. Calculate the number of moles in 5.85g of NaCl. 2. Calculate the number of moles in 30g of SiO2. 3. Calculate the number of moles in 50g of (NH4)2SO4. 4. Calculate the number of moles in 340g of NH3. Culloden academy chemistry department 9
5. Calculate the mass of 5 moles of Na2SO4. 6. Calculate the mass of 0.1 moles of CaCO3. 7. Calculate the mass of 0.75 moles of CH4. 8. Calculate the mass of 2.5 moles of (NH4)3PO4. Culloden academy chemistry department 10
Calculations using the mole and concentration n c V where: number of moles c = concentration in mol l -1 V= volume in litres nb to convert cm 3 into litres, divide by 1000 1. Calculate the number of moles in 500cm 3 of 0.1 mol l -1 sodium chloride solution. 2. Calculate the number of moles in 3000 cm 3 of 2 mol l -1 sulphuric acid. 3. Calculate the number of moles in 5 cm 3 of 0.5 mol l -1 sodium hydroxide solution. 4. Calculate the number of moles in 200cm 3 of a 4 mol l -1 lithium hydroxide solution. 5. Calculate the concentration of a 200cm 3 solution containing 0.1 moles of a solid. Culloden academy chemistry department 11
6. Calculate the concentration of a 50cm 3 solution containing 0.05 moles of a solid. 7. Calculate the concentration of a 3000cm 3 solution containing 2 moles of a solid. 8. Calculate the concentration of a 10cm 3 solution containing 0.004 moles of a solid. 9. Calculate the volume of a solution containing 0.1 moles of a solid with a concentration of 0.5 mol l -1. 10. Calculate the volume of a solution containing 0.05 moles of a solid with a concentration of 1mol l -1. 11. Calculate the volume of a solution containing 2 moles of a solid with a concentration of 10 mol l -1. 12. Calculate the volume of a solution containing 0.4 moles of a solid with a concentration of 0.25 mol l -1. Culloden academy chemistry department 12
Calculations using the mole, gfm and concentration m n gfm where: m = mass, in grams number of moles gfm = gram formula mass n c V where: number of moles c = concentration in mol l -1 V= volume in litres nb to convert cm 3 into litres, divide by 1000 1. The gram formula mass of phosphoric acid is 98g. If 49 g phosphoric acid is dissolved in water and the solution is made up to 200 cm 3, what is the concentration of the resulting solution? 2. 52.5 g of pure citric acid (gfm 210 g) is dissolved in water and the solution is made up to 500 cm 3. What is the concentration of the resulting solution? Culloden academy chemistry department 13
3. What mass of pure sodium nitrate is needed to make 1 litre of solution, concentration 0.2 mol l -1? 4. The formula mass of sulphuric acid is 98 g. What mass of pure sulphuric acid is required to make 100 cm 3 of solution, concentration 0.2 mol l -1? 5. What mass of sodium chloride, NaCl, is required to make 250 cm 3 of a solution with a concentration of 0.5 mol l -1? 6. What is the concentration of Mg(NO3)2 (aq) if 29.7g of solid is dissolved and made up to 500 cm 3? Culloden academy chemistry department 14
Calculating rate of reaction from a graph Change in y-axis Rate = = Change in x-axis y2 y1 x2 x1 e.g. Rate = Change in mass Change in time Rate = Change in gas volume Change in time Units are dependent on units of x and y axes e.g. g s -1, g min -1, cm 3 s -1, l s -1 Culloden academy chemistry department 15
1. Mass / g time / min Calculate the average rate of reaction, in g min -1, over the following times periods: a) 0 200 minutes b) 400 800 minutes c) 600 1200 minutes d) 0 2000 minutes Culloden academy chemistry department 16
2. Calculate the average rate of reaction, in cm 3 s -1 over the following times periods: a) 0 5 seconds b) 10 20 seconds c) 10 40 seconds d) 25-50 seconds Culloden academy chemistry department 17